1. Field of the Invention
The present invention relates to a correction information generation method and a correction information generation apparatus for performing Flat-Field Correction of X-ray detection sensitivity on a pixel detector.
2. Description of the Related Art
It is called Flat-Field Correction to correct sensitivity that is different by pixel in a pixel detector so that actual sensitivity becomes virtually uniform. Flat-Field Correction of the pixel detector, which is carried out by normalizing the values of counts read by each pixel, is effective to one or more dimensional detectors.
When a detector is irradiated with a uniform X-ray, readout channels of each pixel would measure the same number of counts. However, difference in sensitivity parameters by each pixel will occur due to difference in sensitivity, and the number of counts will differ by pixel. In order to reduce such an effect, Flat-Field Correction is carried out.
In a standard correction procedure, counts of all pixels are measured by radiating uniform X-rays to a detector and the measured values are normalized. That is, by ensuring that the whole of the detection surface is irradiated with X-rays at the same intensity by arranging an X-ray beam source and the detector while keeping the long distance between them to make X-rays as uniform as possible, and correction coefficients are calculated based on the premise that the obtained values of counts should actually have the same intensity.
FIG. 8 is a schematic perspective view illustrating a conventional method for correcting sensitivity of a detection pixel. As illustrated in FIG. 8, in the above described procedure, the detector is irradiated with an X-ray from an X-ray beam source through a beam pathway by a helium chamber designed so as to minimize spatial scattering of the X-ray.
On the other hand, there are also patent documents proposing a correction method. In Patent Document 1, as a conventional technology for correcting time degradation of a reference light source, a method, which carries out a correction procedure using data when an accumulative phosphor sheet is uniformly exposed with X-rays, is disclosed. In Patent Document 2, a method, which carries out sensitivity correction by a step of uniformly exposing an accumulative phosphor sheet by transferring the sheet while shuttling an X-ray generation apparatus in a width direction, is disclosed. In Patent Document 3, a method, which reduces dead pixels by the steps of recording a first data set, then, sliding a detection face to record a second data set, and superimposing the second dataset on the first dataset, is disclosed.